Researchers from Kanazawa College, the College of Tokyo, and HORIBA, Ltd. have proven that the preliminary state of platinum-on-carbon (Pt/C) catalyst particles earlier than they’re blended with an ionomer strongly influences how a polymer electrolyte gasoline cell (PEFC) catalyst ink subsequently develops.
Catalyst layers are among the many most vital parts of PEFCs as a result of the electrochemical reactions liable for energy technology happen there. They’re generally fabricated from catalyst inks containing Pt/C catalyst, ionomer, and solvents. In Pt/C catalysts, platinum nanoparticles are supported—that’s, finely dispersed and immobilized—on the floor of carbon particles.
Earlier research of catalyst-ink preparation have primarily targeted on elements corresponding to solvent composition, ionomer content material, dispersion methodology, and mixing time. Nonetheless, a lot much less consideration has been paid to the state of the Pt/C catalyst earlier than the ionomer is added.
The analysis staff due to this fact launched a managed pre-mixing step through which Pt/C catalyst was blended with deionized water for various durations earlier than ionomer addition. This produced totally different preliminary Pt/C mixture states. After including the ionomer and ethanol, the researchers ready catalyst inks utilizing totally different main-mixing instances and evaluated their particle-size distributions, rheological properties, elemental composition by SEM-EDX, and electrochemical floor space (ECSA).
With out pre-mixing, the Pt/C catalyst initially contained comparatively giant agglomerates. These constructions have been steadily damaged down throughout subsequent principal mixing, and the ECSA elevated as mixing continued.
In distinction, short-time pre-mixing produced smaller and comparatively uniform Pt/C aggregates earlier than ionomer addition. This preliminary state facilitated subsequent dispersion, and the very best ECSA within the research, 64.42 m² gPt−1, was obtained after 1 hour of principal mixing.
Lengthy-time pre-mixing produced a broader particle-size distribution according to re-agglomeration. Even after extended principal mixing, a fraction of the bigger Pt/C constructions remained immune to additional breakup. The mixed particle-size, rheological, SEM-EDX, and electrochemical outcomes point out that these persistent constructions restricted the electrochemical accessibility of Pt surfaces and resulted in decrease ECSA.
The findings exhibit that catalyst-ink processing is set not solely by how the ink is blended in spite of everything parts are mixed, but additionally by the preliminary state of the catalyst earlier than ionomer addition. Controlling this preliminary Pt/C mixture state due to this fact supplies a further course of parameter for designing catalyst inks with reproducible microstructural and electrochemical properties.
Researcher Quote
“Catalyst-ink analysis has historically targeted on how the ink is blended in spite of everything of its parts are mixed,” mentioned Takuya Tsujiguchi, Professor at Kanazawa College. “Our outcomes present that what occurs earlier than that stage additionally issues. By controlling the preliminary state of the catalyst, we are able to affect how the ink evolves throughout subsequent mixing. This provides us a brand new course of variable for understanding and finally optimizing catalyst-ink manufacturing.”
Towards autonomous optimization of catalyst-ink processing
The findings will even contribute to the event of Mixing and Dispersion ROPES (Robotic Goal Course of Exploration System), which is being collectively developed by Kanazawa College, the College of Tokyo, and HORIBA, Ltd. below a NEDO-funded undertaking.
Mixing and Dispersion ROPES is designed to guage the dispersion and aggregation states of particles in fuel-cell catalyst inks utilizing a number of analytical and measurement strategies and to make use of the ensuing knowledge to robotically and autonomously discover optimum mixing and dispersion circumstances. Kanazawa College is liable for elucidating the underlying mixing and dispersion mechanisms.
The current research supplies mechanistic perception into one vital course of variable—the preliminary Pt/C mixture state—and the way it impacts subsequent dispersion and electrochemical Pt accessibility. Integrating such mechanistic understanding with particle-size, rheological, and different measurement knowledge is anticipated to assist refine the method variables and analysis standards utilized in autonomous exploration. Finally, this method goals to speed up and enhance the event of producing processes for fuel-cell catalyst layers.
